Quick Facts

Quick facts

  • American Rat's Tail Grass (Sporobolus jacquemontii) is a tufted perennial grass growing to 75 cm.
  • It is of tropical American origin and in Australia can be found in Queensland, Western Australia and the Northern Territory.
  • It invades pastures replacing more productive grass species.
  • American Rat's Tail Grass is very similar in appearance to Giant Rat's Tail Grass (S. pyramidalis).
  • Control strategies for American Rat's Tail Grass include pasture improvement, stock and grazing control and use of herbicides.

What Does It Look Like?

What is it?

American Rat's Tail Grass (Sporobolus jacquemontii) is a tufted perennial grass with stems growing to 50–75 cm high and 1–2 mm diameter wide at the base. The leaf blades are 1.2–2.5 mm wide (Clayton et al. 1974).

The spike-like flower head grows to 25 cm long and 0.5–3 cm wide (Land Protection 2007) with branches that are held loosely against the main axis, the lower ones 3–4 cm long. The flower clusters are 1.8–2 mm long and the upper bract (glume) is rounded at the apex. The seed is 1–1.1 mm long and slightly flattened at the top (Clayton et al. 1974).

For further information and assistance with identification of American Rat's Tail Grass contact the herbarium in your state or territory.

Flower colour

Green, Brown

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

American Rat's Tail Grass grows in the warm moist sub-tropics of Australia (AVH 2008). The specimens found in Western Australia were collected from the bank of a creek with a permanent pool and a lawn near a picnic area, both in the state's far north (Western Australian Herbarium 2003). In Queensland it occurs as a weed of poor pastures and on roadsides and urban areas (Simon 2008 pers. comm.)

Are there similar species?

American Rat's Tail Grass is very similar in appearance to Giant Rat's Tail Grass (S. pyramidalis) and even experts have difficulty differentiating the two (Department of Primary Industry and Fisheries, Queensland 2007). There is almost no difference in size and shape of their flower clusters but American Rat's Tail Grass is much shorter, growing to 0.75 m high compared to 1.7.m for Giant Rat's Tail Grass (Simon 2005). American Rat's Tail Grass is therefore easily mistaken for a smaller, less robust specimen of Giant Rat's Tail Grass making it very difficult the separate them (Burkhill 1985).

Weedy Sporobolus grasses are difficult to distinguish from other pasture grasses before maturity, however the leaves are noticeably tougher than any other species. The seeds of all species are indistinguishable in pasture seed samples using current seed sample identification techniques (Land Protection 2007).

Why Is It A Weed?

What are its impacts?

Agriculture: American Rat's Tail Grass does not present as serious a problem as Giant Rat's Tail Grass (Sporobolus pyramidalis and S. natalensis) in Australia, but its presence indicates depletion of pasture quality (Simon 2005). It invades pastures, replacing more productive types of grasses (Department of Primary Industry and Fisheries, Queensland (2007).

Other species of Sporobolus grasses can quickly dominate a pasture, especially following overgrazing or soil disturbance. Mature leaf blades are tough and difficult for cattle to graze. Tough leaves and stems have been known to loosen teeth of cattle and horses whilst grazing. These grasses can also become a serious fire hazard (Land Protection 2007).

How does it spread?

There is no specific information available on the dispersal of American Rat's Tail Grass, but like other Sporobolus species, the mature seed has a loose outer coat which becomes sticky when wet (Jacobs & McClay 1993). This enables the seed to stick to animals and humans and can be spread in soil on machinery and vehicles (Land Protection 2007).

What is its history in Australia?

It is not known when or how American Rat's Tail Grass arrived in Australia.

How To Manage It?

Best practice management

Control strategies for American Rat's Tail Grass, as with all the weedy Sporobolus species, include maintaining pastures in a vigorous and dense condition, controlling stock movement and grazing, cleaning machinery, slashing, and spraying with herbicides (Land Protection 2007).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Biological control: No biological control agents for Parramatta Grass are currently available in Australia; however, investigations into possible agents are underway (CRC for Australian Weed Management 2003).

A draft of the weedy Sporobolus best practice manual, which includes principles of grazing management as they apply to weedy Sporobolus grasses is available at http://www.weeds.crc.org.au/text_ver/projects/proj_3_2_4_2.html 

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

American Rat's Tail Grass flowers all year (Simon 2005).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

American Rat's Tail Grass occurs from Cape York to south-eastern Queensland, with isolated records from the Northern Territory and the Kimberley region of Western Australia (Simon 2005).

Where does it originate?

American Rat's Tail Grass is of tropical American origin and occurs also in Africa (Sierra Leone to West Cameroons) (Burkhill 1985).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Sporobolus jacquemontii

Other scientific names (synonyms)?

  • Sporobolus pyramidalis var. jacquemontii (Kunth) Jovet & Guedes
  • Vilfa jacquemontii Kunth ex Trin.

Does it have other known common name(s)?


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